<!DOCTYPE html>
<html lang="en">
<head>
	<meta charset="UTF-8">
	<title>Document</title>
	<style>
		div{
			width: 200px;
			height: 200px;
		}
		.box1{
			background:red;
		}
		.box2{
			background:rgb(25,56,89);
		}
		.box3{
			background:#A3E22B;
		}
		.box4{
			background:rgba(25,56,89,0.5);
		}
	</style>
</head>
<body>
	<div class="box1">box1</div>
	<div class="box2">box2</div>
	<div class="box3">box3</div>
	<div class="box4">box4</div>
</body>
</html>